Conventionally, there is known a technique in which a diesel particulate filter (or NOx catalyst) is provided in an exhaust passage of a diesel engine as an exhaust gas purifying device (postprocessing device), and exhaust gas discharged from the diesel engine is purified by the diesel particulate filter (or NOx catalyst) (see patent documents 1, 2 and 3). There is also known a technique in which a filter case (inner case) is provided in a casing (outer case) and a particulate filter is disposed in the filter case.